The present invention relates to an internal-combustion engine having a pressure lubrication system according to the dry-sump principle, particularly for an opposed-cylinder engine.
In today's water-cooled 6-cylinder horizontally opposed engines of the Porsche 911 Carrera series, an oil partition box is provided in the oil bearing housing or in the oil pan and is fastened to the oil pan lid. The oil sump for the lubricating oil supply of the engine is constructed in this oil partition box. The lubricating oil returned from the consuming devices into the oil pan is first returned outside the oil partition box forming the oil scavenging space before it flows into the actual oil scavenging space via openings monitored in the oil partition box by flaps.
In engines with a dry-sump lubrication, the oil flowing back into the oil pan is delivered by a scavenging pump into a separate oil tank or oil storage tank. The pressure oil feed pump removes the lubricant from there by suction and presses it by way of filters and, if required, oil coolers to the lubricating points. In most cases, the oil tank is fastened on the outside to the crankcase and has corresponding connections for the externally laid pressure oil pipes.
An object of the present invention is to provide a low-friction driving mechanism with a dry-sump pressure lubrication system, particularly for the high rotational speed operation, in which the return or circulation times for lubricating oil are shortened, for increasing the specific power of an internal-combustion engine. In addition, the components required for the pressure lubrication system of the internal-combustion engine are to be largely integrated in the engine in a space-saving manner.
According to the invention, this object is achieved by integrating the dry and wet sump space in the internal-combustion engine crankcase. As a result, the oil tank or oil storage tank required for the dry-sump lubrication can be integrated in a space-saving manner directly in the engine, so that the otherwise normally required externally laid oil pipes are largely eliminated. The circulating paths and therefore the circulating times for the lubricating oil are therefore shortened so that, even at high lateral or longitudinal accelerations of the vehicle, a sufficient lubricating oil supply is ensured.
In a first advantageous embodiment, the oil storage space forming the wet sump is arranged directly below the dry-sump space. For this purpose, for example, the oil lid closing off the dry sump space in the downward direction has a double-walled construction. An oil scavenging snorkel leading to the main oil pump of the engine is placed at the floor of the forming hollow space. Furthermore, the hollow space receiving the lubricating oil is equipped with a connection which is connected with the delivery side of the dry-sump oil return pump.
In a second advantageous embodiment, the oil storage space forming the wet sump is integrated directly in the crankcase and is separated from the dry-sump space by one or more partitioning walls. This offers a solution, for example, for an opposed-cylinder engine, because of the horizontally arranged cylinder for the oil return into the wet sump. In this solution, an oil partition box forming the dry space is arranged in the crankcase such that (wet sump) collecting spaces for the lubricating oil removed by suction from the oil partition box remain on the left and the right of the oil partition box. The two collecting spaces are connected with one another by a space between the oil pan lid and the floor of the oil partition box.
For the defoaming or venting of the lubricating oil, the lubricating oil removed by suction from the dry-sump space and the cylinder heads is delivered into the wet sump by a central oil/air separator.
Another aspect of the invention consists of the fact that annular spaces around the cylinders are utilized for returning the oil into the wet sump collecting spaces. Particularly in the case of cylinder crankcases of an open-deck construction, where the water cooling jacket is formed only in the upper portion of the cylinders, an annular space remains which is open toward the crankcase space and which, with a corresponding face-side sealing, can be utilized as part of the oil return pipe into the wet sump. Since the wet-sump collecting space(s) are arranged below the annular spaces utilized for the oil return, by way of corresponding openings, the lubricating oil can flow from the annular spaces directly into the collecting space(s). This largely eliminates external oil pipes, so that this measure contributes to a compact and cost-effective conversion of an internal-combustion engine with a dry-sump lubrication.
Because of the horizontally arranged cylinders, the annular spaces used for the lubricating oil return can be vented in the upward direction. This achieves a defoaming of the lubricating oil, and the above-described oil/air separator may not be necessary.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.